Conventional office chairs frequently include a seat-back arrangement which is connected to a base by a tilt mechanism. The tilt mechanism defines one or more pivot axes about which a seat or back assembly may pivot or tilt relative to the base. Office chairs typically tilt rearwardly about fixed horizontal pivot axes wherein the seat and back assemblies are rearwardly tiltable either together or independently. To resist such tilting and bias the seat and back assemblies to normal upright positions, numerous tilt mechanisms have been provided which include springs such as coil, leaf and torsion springs which oppose the tilting movement.
As an alternative to conventional spring arrangements, prior tilt control mechanisms have also used elastomeric pads or rings between relatively moving surfaces. The pads or rings are resilient so as to be compressed between the moving surfaces to resist the tilting movement. Some of these tilt mechanisms permit the seat to pivot in multiple directions.
Examples of chairs using elastomeric pads or rings which permit tilting in multiple directions are disclosed in U.S. Pat. Nos. 139,948, 3,309,137, 4,027,843, and 5,573,304. The 3,309,137 patent permits adjustment of tilting resistance by varying the compression of an elastomeric ring. The chairs disclosed in the remaining patents do not permit adjustment of the tilting resistance.
In another chair as disclosed in U.S. Pat. No. 4,890,886, the tilt control mechanism defines a fixed pivot axis between the seat assembly and the chair base. The tilt control mechanism further includes a plate secured to the seat assembly so as to move with the seat assembly relative to the base, and a second plate which is spaced apart from the first plate and remains stationary relative to the base. These opposing plates move relative to each other during tilting of the seat assembly, and elastomeric pads are provided between these relatively movable plates to resist tilting and bias the seat assembly to a neutral position. To adjust resistance to tilting, the elastomeric pads are movable relative to the pivot axis to thereby adjust the distance defined therebetween. In one embodiment, the pads are vertically movable.
However, users, such as office workers, who sit in such chairs typically move in all directions, such as sidewardly, forwardly and rearwardly when working. Conventional tilt control mechanisms having fixed axes, however, restrict such movement due to the fixed axes, and hence do not readily accommodate the usual movements of a user such as movement to the side.
To more readily accommodate the various movements of a user, the chair of the present invention accommodates movement of a user both forwardly and sidewardly and in fact permits the chair seat to swivel about a connection point so as to react to the user. In particular, to overcome the disadvantages of conventional chair designs which use fixed pivot axes, the chair of the present invention includes a tilt control mechanism which permits universal tilting or swiveling of the seat assembly relative to the base in substantially all horizontal directions. The seat assembly is not restrained by fixed pivot axes but instead effectively pivots about a pivot or connection point. Thus, the seat assembly can pivot forwardly and rearwardly, sidewardly and in any other horizontal direction extending radially away from the pivot point, and can also be swivelled about the connection point. Thus, as a user shifts and moves, the chair reacts to the user's movements while still providing sufficient resistance to the universal tilting movement to provide stability and control for the user.
The tilt control mechanism of the invention, in an embodiment thereof, includes a support member which extends upwardly from the pedestal of the base. The support member has a bearing at the top thereof which pivotally supports a pivot bracket mounted on the seat assembly. The cooperating bearing and pivot bracket effectively define a pivot point, rather than a fixed horizontal pivot axis, about which the seat assembly pivots or swivels such that the seat assembly pivots in substantially all radial directions extending away from the pivot point.
To provide resistance to such tilting while providing stability for the user, the tilt control mechanism in a preferred embodiment includes a cylindrical housing which is disposed in concentric and surrounding relationship to the support column wherein the housing is spaced radially outwardly from the support column to define an annular clearance space therebetween. An elastomeric doughnut-shaped ring is disposed within this annular clearance space whereby the ring is disposed concentric with the column and housing and extends radially therebetween. As the housing moves with the seat assembly relative to the column, the elastomeric material of the resilient ring is compressed and limits the tilting, and restores the seat assembly to the initial neutral position.
The tilt control arrangement also permits adjustment of the tilting resistance to accommodate various size users or working conditions. The tilt control mechanism includes an adjustment mechanism connected to the resilient ring which allows a user to selectively move the resilient ring toward and away from the pivot point, whereby the effective resistance to tilting is increased or decreased.
The adjustment mechanism in this embodiment includes a drive ring or cylinder having an inclined groove or track, and an intermediate connector which is slidably connected to the inclined groove. As the intermediate connector slides along the inclined groove during rotation of the drive ring, the intermediate connector moves vertically. The intermediate connector is connected to the resilient ring to move vertically therewith. The connection of the intermediate connector to the inclined groove translates rotational movement of the drive ring into vertical movement of the resilient ring to thereby adjust the position of the resilient ring relative to the pivot point. Since the resilient ring effectively applies a biasing force to the housing as the resilient ring is compressed, this vertical movement of the resilient ring adjusts the location at which the force of the resilient ring acts relative to the pivot axis.
This pivot or tilt control arrangement thereby permits tilting of the seat assembly in any direction which extends radially away from the pivot point. Further, the tilting resistance can be conveniently adjusted by a person seated in the chair.
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.